/Engine/Source/Editor/ContentBrowser/Public/IContentBrowserSingleton.h
Capture active viewport to thumbnail and assigns that thumbnail to incoming assets
void CaptureThumbnailFromViewport ( [FViewport](API\Runtime\Engine\FViewport) * InViewport, [TArray](API\Runtime\Core\Containers\TArray)< [FAssetData](API\Runtime\CoreUObject\AssetRegistry\FAssetData) > & SelectedAssets )